High speed rotating apparatuses are often driven by electric motors or internal combustion engines. Superchargers are a high speed device which is typically driven directly by an internal combustion engine. In such cases a speed increasing gear box or belt drive is needed. Such superchargers are limited to a relatively low rotating speed and are large in size. Paxton Blowers and Vortech Engineering Co. are marketing such superchargers. Fixed gear ratio superchargers suffer from two very undesirable features which are: 1) there is a sharp decrease in boost pressure at low engine RPM because boost pressure goes to the square of the speed of rotation, and 2) it is generally not feasible to disconnect the blower from the engine when the supercharger is not needed.
There is a great need in the engine industry for efficient hydraulic systems for driving compact, light weight superchargers. According to an article at page 27 of the August 1993 issue of Popular Science, Miller cycle engines, developed by Mazda "requires a compact, high-efficiency air compressor-conventional turbochargers and superchargers just can't generate the volume of air required". The article further states, "Mazda teamed with heavy equipment manufacturer Ishikawajima-Harima Heavy Industries Co. to develop a belt driven, screw-type compressor supercharger. The new supercharger is expensive, which is one reason Mazda doesn't plan to use the Miller-cycle engine in small cars. Lean-burn technology makes more sense there."
It is known that low pressure at hydraulic pump inlets can cause cavitation and foaming which can lead to lower efficiencies and shorten pump life.
Turbochargers of many designs are driven by engine exhaust. One such model is Model To 4B 3S supplied by Turbonetics Inc. This unit produces a compressor ratio (output pressure/atmospheric pressure) of 1.52. The various parts of this unit can be purchased separately from Turbonetics as listed in its catalog.
Gear driven and belt driven oil pumps are commercially available in the 10 to 20 HP range for producing oil pressures in the range of 1,000 to 2,500 PSIG at flows of 20 to 40 GPM.
The Applicant has been issued a U.S. Pat. No. 5,013,214 for a high speed water driven fan. Disclosed in the specification was a turbine which produced 4 horsepower at 10,000 RPM. The specification referred to and provided guidance for increased horsepower designs and higher RPM's. The hydraulic design of the present invention is based on extensive tests of the Applicant's high speed water turbine driven high velocity fan with water pressure differentials of up to 450 psi and generating 19.6 HP at 14,250 RPM. Relatively low stress levels and low operating temperature of the reference fan turbine wheel has allowed for the 2.07 inch diameter wheel to be made entirely of Delrin type plastic.
It is known that plastic turbines are generally less expensive to produce than metal turbines, but at very high rotating speeds and high temperatures plastic turbines do not have sufficient strength to provide reliable performance. For very small steel turbine wheels, standard milling procedures are not feasible and electro discharge machining is typically utilized which is very expensive. Typical production costs of making a 0.80 inch diameter turbine wheel with 34 blades is on the order of $300. Sintering is another possibility, but its tooling costs and development risks would be very high.
Utilization of high temperature thermoplastics to make very high speed turbine wheels would lower the cost significantly since the blades could be milled with conventional techniques, but the combined effects of high centrifugal stresses and high oil temperatures would cause the plastic to deform and creep with time, especially in the hub area where precision fit between the shaft and the wheel bore is required at all times.
It is known that a significant advantage of superchargers over turbochargers is that the superchargers respond immediately to increased engine power whereas turbochargers tend to lag on acceleration. Superchargers driven by an oversized oil pump can actually anticipate increased demand for engine power by controlling the oil pressure to react with the accelerator. For motor vehicle superchargers high turbine efficiencies, low cost and long life expectancies are all of paramount importance.